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.TH THR_JOIN 3C "Mar 27, 2000"
.SH NAME
thr_join \- wait for thread termination
.SH SYNOPSIS
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR...[ \fIlibrary\fR... ]
#include <thread.h>

\fBint\fR \fBthr_join\fR(\fBthread_t\fR \fIthread\fR, \fBthread_t *\fR\fIdeparted\fR, \fBvoid **\fR\fIstatus\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBthr_join()\fR function suspends processing of the calling thread until
the target \fIthread\fR completes. The \fIthread\fR argument must be a member
of the current process and cannot be a detached thread. See
\fBthr_create\fR(3C).
.sp
.LP
If two or more threads wait for the same thread to complete, all will suspend
processing until the thread has terminated, and then one thread will return
successfully and the others will return with an error of \fBESRCH\fR. The
\fBthr_join()\fR function will not block processing of the calling thread if
the target \fIthread\fR has already terminated.
.sp
.LP
If a \fBthr_join()\fR call returns successfully with a non-null \fIstatus\fR
argument, the value passed to \fBthr_exit\fR(3C) by the terminating thread will
be placed in the location referenced by \fIstatus\fR.
.sp
.LP
If the target \fIthread\fR \fBID\fR is  \fB0\fR, \fBthr_join()\fR finds and
returns the status of a terminated undetached thread in the process. If no such
thread exists, it suspends processing of the calling thread until a thread for
which no other thread is waiting enters that state, at which time it returns
successfully, or until all other threads in the process are either daemon
threads or threads waiting in \fBthr_join()\fR, in which case it returns
\fBEDEADLK\fR. See \fBNOTES\fR.
.sp
.LP
If \fIdeparted\fR is not \fINULL\fR, it points to a location that is set to the
ID of the terminated thread if \fBthr_join()\fR returns successfully.
.SH RETURN VALUES
.sp
.LP
If successful, \fBthr_join()\fR returns \fB0\fR. Otherwise, an error number is
returned to indicate the error.
.SH ERRORS
.sp
.ne 2
.na
\fB\fBEDEADLK\fR \fR
.ad
.RS 12n
A joining deadlock would occur, such as when a thread attempts to wait for
itself, or the calling thread is waiting for any thread to exit and only daemon
threads or waiting threads exist in the process.
.RE

.sp
.ne 2
.na
\fB\fBESRCH\fR \fR
.ad
.RS 12n
No undetached thread could be found corresponding to the given thread ID.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR thr_create (3C),
.BR thr_exit (3C),
.BR wait (3C),
.BR attributes (7),
.BR standards (7)
.SH NOTES
.sp
.LP
Using thr_join(3C) in the following syntax,
.sp
.in +2
.nf
while (thr_join(0, NULL, NULL) == 0);
.fi
.in -2

.sp
.LP
will wait for the termination of all non-daemon threads, excluding threads that
are themselves waiting in \fBthr_join()\fR.
